The present invention relates generally to an apparatus and method for heating and spinning feedstock materials. More particularly, the present invention relates to an improved apparatus and method for heating and spinning solid, non-solubilized feedstock material capable of undergoing intraparticle flow with the application of heat and force such as corn syrup solids, sucrose, polymers and the like where the heating of such materials is external to a spinning apparatus.
Various machines have been devised for the melting and spinning of meltable materials, especially sugar through a "melt spin" process. A particularized form of the melt spin process is known as flash flow processing. This process is described in U.S. Pat. Nos. 4,855,326; 5,279,849 and 5,387,431 all of which are incorporated herein by reference. The feedstock material may be introduced into a spinning head of the spinning machine in solid form. The material is subjected to heat therein just prior to being spun out from the spinner head where it reforms and solidifies in the air.
Typical cotton candy spinning machines operate by a melt spin process and include a spinner head having a generally cylindrical apertured wall. Sugar in solid form, is introduced into the spinner head where it is melted. Spinning of the spinner head causes the melted sugar to be spun out through the apertures in the cylindrical wall where it solidifies into a floss-like structure which has become to be known as cotton candy. The characteristic shape and consistency of the spun material is influenced by several factors. These factors include the size and construction of the spinner head, the size, arrangement and location of the apertures in the cylindrical wall of the spinner head, as well as the manner in which heat is applied to the spinner head.
Numerous machines, designed specifically for spinning cotton candy, have employed various modifications of the spinner head construction in an effort to yield spun product.
U.S. Pat. No. 4,872,821 discloses a cotton candy spinning machine including a spinner head having stacked, slotted, cylindrical walls and coiled heating elements adjacent each wall. Sugar in solid form is introduced into the spinner head and propelled against the heating elements where it is melted. The molten sugar is spun out through the slots where it solidifies into the floss-like material known as cotton candy.
U.S. Pat. No. 3,930,043 discloses a machine which includes a helical resistance heating element positioned within a finely perforated shell. The heating element is supported against the inner wall of the shell by spacer elements. As the shell spins, molten sugar is extruded through the perforations. Similar machines are disclosed in U.S. Pat. Nos. 3,073,262 and 3,070,045.
U.S. Pat. No. 3,856,443 discloses another type of spinning machine wherein the perforated shell through which sugar is extruded functions as the resistance element of the heating means.
U.S. Pat. No. 1,489,342 discloses a spinner head having an annular heating element formed of a strip of electrical resistance material. The strip is bent as a flat spiral structure forming slanted stretches of heating element having narrow slots between them. The heating element melts the sugar which then passes through the slots between the stretches of the heating element and out through an apertured shell positioned thereabout.
While some of the above described machinery may perform satisfactorily for converting granular sugar into a floss-like material in the formation of cotton candy, it does not function entirely satisfactorily for spinning other materials which may have properties quite dissimilar to sugar or for other materials mixed with sugar, or for liquiflash processing. Nor does the above-described machinery have the capacity to yield product having a desired shape and size. In recent years, it has been increasingly desirable to spin not only feedstock such as sugar and materials combined with sugar, but also non-saccharides.
Attempts have been made to eliminate undesirable drawbacks of conventional machinery especially with regard to the spinning of feedstock including non-sugars as well as sugars combined with non-sugars, is shown and described in U.S. Pat. No. 5,427,811, which is incorporated by reference herein. The spinner head described therein is referred to as a "cable head" spinner. The cylindrical wall of the spinner head is formed by a heating element comprising a cable which is helically wound about the axis of rotation of the spinner head. In this way the heating element itself is used as the wall of the spinner head through which the material is ejected. U.S. Pat. No. 5,458,823, which is also incorporated by reference herein, attempts to solve the problem of non-uniform heating of the feedstock by incorporating discrete closely spaced elongate heating elements. The elements are peripherally spaced about the spinner head and may be individually heated in order to control the morphology of the of the expelled material.
All previously designed spinner heads for producing a spun product through a melt spin process, including flash flow and liquiflash processing have contained heaters built into the head. Such designs require considerable head mass for heater enclosure resulting in the loss of surface area for expelled product. In addition, power must be supplied to the rotating heaters. These requirements present significant obstacles to the scale up and production of larger and faster heads for both bead and floss production.
Many prior art spinner heads including the cable head utilize electrical resistance coils located on the spinning head in order to heat the material. Such head based heating sources limit the ability to focus the heat to the outermost surface of the head. The elements have a certain thickness over which the material must pass prior to expulsion. In addition the coils tend to heat the entire wall through conduction even if the coils are mounted on the wall's outer surface. This creates a heated flow path that may over heat the material leading to agglomeration.
In addition, many other problems and limitations arise in supplying electrical current to the rotating spinner head. Typically, current is supplied to rotating devices using a set of contacts or brushes located on the rotating device which frictionally engage a stationary ring to which power is supplied. Use of these components adds a extra degree of complexity to the head and present certain limitations.
The components, especially the contacts, have a finite working life after which they must be replaced. The contacts' life expectancy is inversely proportional to the amount of current carried therethrough. This presents a limitation to increasing the size of the spinning head since larger heads require more power, and therefore, more current. It is desirable to increase the spinner head size in order to both increase the yield of reformed product per head as well as to produce certain reformed morphologies. Large spinner heads, however, have previously not been feasible to employ due in part to the high maintenance cost associated with the low life cycles of the contacts. Furthermore, the life expectancy of the contacts is inversely proportional to the rotational velocity of the head due to the frictional engagement of the current transmitting components. Therefore, in order to maintain reasonable life expectancies the rotational velocity must be limited. This too limits the yield per head and morphologies that can be produced.
Additionally, the shape of the wall is very important in determining the morphology of the reformed product. It is desirable, therefore, to have as much design flexibility in the wall in order to create a variety of morphologies. As previously stated, incorporating a heating means such as heating elements or coils into the wall places constraints on the design of the processing wall, thereby limiting the variety of morphologies which can be produced. Head mounted heater coils also reduce the surface area that is available for exit points from which material may be expelled.
Another disadvantage of spinner head mounted heating means is the increased weight it encompasses. The heavier the head the more substantial the support and mounting means that are required to support the rotating load. In addition, the increased weight and complexity of the head mounted heating device increases the likelihood that the head will not be rotationally balanced. If the head is not rotationally balanced the loading on the supports will shift with every revolution resulting in vibration. These vibrations present a problem since they subject the support means, such as the shafts and bearings to stresses, thereby decreasing the service life of the material processing system.
In that regard, a need clearly exists for spinning machinery which provides the user with a means of heating the feedstock material without the limitations inherent in the use of heating coils located on the spinner head.